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The L.S. Starrett Company offers the 649 series spindle square for tramming the head of a vertical milling machine. Tramming ensures squareness and perpendicularity between the spindle and work surface. According to the company, the device improves accuracy and saves time compared to the traditional method of tramming with a dial test indicator.
The spindle square is fully assembled with two AGD Group 2 dial indicators. It has a solid steel body, durable black wrinkle finish and ground gaging surface. The unit weighs approximately 4 lbs and measures approximately 6 ¾" × 5½" (172 × 140 mm) from the top of the shank to the end of the contact points.
To use, a machinist sets the spindle square indicator to “0” on a surface plate and places the spindle square into the milling machine’s collet. The head is brought down to the table until both indicator needles have rotated approximately one full rotation. The needles do not need to point in the same direction. Identical numerical readings, not the needle positions, indicate squareness. Normal tramming procedures are used until both indicators read the same numerical value. After setting the X axis, the same procedure is repeated for the Y axis.